Charge forming device



Oct. 18, 1932. w. H. TEETER Oct. 18, 1932.-

Vl H.TEETER CHARGE FORMING DEVICE 4 Sheets-Sheet 2 Filed July 17, 1928mma Oct. 18, 1932. w. H. TETER dimer.' FoRING DEVICE 4 Sheets-Sheet 3lld July 17, 1928 WN kw Oct. I8, 1932. w. H. TEETER CHARGE FORMINGDEVICE Filed July 17. 1928 4 Sheets-Sheet 4 Patented Oct. 18, 1932UNITED STATES PATENT OFFICE WILFORD H. TEETER, OF .DAYTONQ OHIO, ASSIGNOR, BY MESNE ASSIGNMENTS, T DELCO PRODUCTS CORFORATION,

OF DAYTON, OHIO, A CORPORATION 0F DELAWARE CHARGE FQRMING DEVICEApplication filed July/1'?,

This invention relates to charge forming devices for internal combustionengines, and more particularly to that type of charge forming devicewhich comprises a plurality of primary carburetors for supplying aprimary mixture of fuel and air to a plurality of secondary carbretorslocated adjacent the engine intake ports, and to which additional airmay be supplied under certain operating conditions through a secondaryair passage, for admixture with the primary mixture.

Examples of charge forming devices of this type are disclosed in thecopending applications of lViltord H. Teeter, Serial No. 221,372. liledSeptember 22, 1927, and Fred E. seltine. et al., Serial No. 288,683,filed June 10, 1928.

It is-.the general object of the present invention to provide improvedmeans for controlling the proportions of fuel and air in the mixture,and more particularly, to provide improved means for enriching themixture during the acceleration period, to provide a mixture rich enoughin fuel content to give the necessary power for smooth and rapidacceleration.

More specifically, it is an object of the invention to provide means fortemporarily restricting the admission of secondary air following anyopening movement of the throttle, so that the enriched primary mixtureis delivered to the intake ports without delay and without dilution byan excess of secondary air.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings, wherein a preferred form of embodiment of the presentinvention is clearly shown.

In the drawings: y

Fig. 1 is a plan view of the present invention attached to the enginecylinder head, a part of which is shownV n section.

Fig. 2 is a side elevation looking toward the engine block.

Fig. 3 is a section on line 3-3 of Fig. 1. Fig. 4 is a section online'4--4 ot' Fig. l.

i928. semi no. 293,424.,

Fig. 5 is a fragmentary detail section on the line of Fig. 3. I

Fig. (5 is a detail view of 'the primary throttle valve.

Fig. 7 is a side elevation of the main carburetor unit looking from theright in Fig. 2.

Fig. 8 is a side elevation of the main carburetor unit looking from theleft in Fig. 2. Fig. 9 is a detail sectional view, partly diagrammatic,showing theI means tor retarding the opening ot the secondary air valve.y

Fig. 10 is a section through the secondary mixing chamber on line 10-10of Fig.

Figs. 11 and 12 are detail sections at right angles to each othei; ofthe float valve mechanism and fuel inlet passage controlled thereby.l

Fig. 13 is a detail section on the line 13- 13 of Fig. 3. It will beobserved that the main air passage which admits air to the secondarymixing chambers has yin some instances in this specification been termeda secondary air passage, while the air flowing through such passage hasbeen termed secondary air. These terms have been used to distlnguishfrom. the primary air passage and primary air which goes to the primarymixing chambers.

The device disclosed herein comprises a main air manifold indicated inits entirety by the reference character 10', and having three outletbranches 11, 12 and 13 each of which is adapted to communicate with oneof the .ports 14 of a multicylinder engine. lach port serves twoadjacent cylinders through valve ports 14a and 14?), as clearlyindicated in -'Fig..1. The cylinder head is shown in three separatefragments 15, but it will be understood that it may be an integralstructure. The branches 11, 12 and 13 are each provided with anattaching flange 16, for attaching the manifoldl to the engine block inthe conventional manner. Adjacent the inlet of the manifold is provideda flange 1.7 to which may be secured the main carbure- `tor unit asshown in Fig. 3.

The main carburetor unit comprises a. main houslng in therform ofasingle casting 18, 100

asv

i attached by screws 19 to theiflange 17 An ings to make a tight joint,and a sheet metal nipple 31, screwed into the main housing 18 .castinand the drill hole on the opposite fuel bowl 27 is held tight against ashoulder 28 on said main hous1ng`18 by means of a screw 29 which isscrewed into a post 30 de- I pending from and integral with the casting25.

A fuel line leading to a main source of fuel supply (not shown) isconnected to a as shown in Fig. 1. This nipple may have a screen securedtherein in a manner well known so that incoming fuel must pass throughthe screen and said ni ple communicates with a bore 32 formed 1n thewall of housing 18, the bore 32 connecting with bore 33 also in the wallof said housing as shown in Fig. 12. At its inner end the bore 33connects with a vertical bore 34,. which in turn `communicates with abore 35 in casting 25.

. A plug 36'is screwed into the lower end of connects-with each of thenozzles 42 through bore 35 and is provided with lateral fuel outlets 37through which the fuel Hows into the float chamber. Cooperating withvalve seat 38 is a valve 39 controlled by a oat 40 pivoted at 41. Thevalve operates in the usual manner to maintain a constant fuel level inthe said float chamber.

Fuel is conducted from the fuel bowl to a plurality of vprimary fuelnozzles 42 located in the primary mixing chambers 43 formed in thecentral part of t e main housing which may be termed the distributorblock. The construction of the distributor block and co` operatingelements comprising the primary carburetors will vbe more fullydescribed hereinafter. To permit the fuel to flow from the fuel bowl tothe primary nozzles 42the casting 25 is rovided with a vertical fuelchannel 44 which communicates at its uplp'er endwith a horizontalfuel'canal 45 w 1ch holes 46. Fuel is admittedA from the fuel bowl tothe channel 44 at low speed through a metering orifice 47. All of thefuel flowing to the fuel nozzles 42 u to a certain predetermined enginespeed, or example that corresponding to a vehicular speed of 20 milesper hour passes throleilgh the metering orifice 47. For hi her spe sthan said predetermined speer? fuel is also admitted to the fuel channel44 through an orifice 48 controlledv by a fuel valve 49, operated in amanner fully described hereinafter, and thence through ka.

horizontal channel 50, connecting with the lower end of channel 44.

Fuel is lifted from the fuel bowl through the nozzles 42 to the primarAmixing chambers by the suction therein. hen the throttle is movedtoward closed position to reduce the engine speed there is a suddenreduction in suction on the vertical column of fuel between the fuelbowl and the nozzle which mlght permit this column of fuel to drop suf-`iciently to cause a temporary fuel starving of the engine unless meanswere provided to prevent the dropping of such column of fuel. To preventthis action a check valve 51 is received in an enlarged chamber 52 atthe junction of channels 44 and 45 and on reduction of suction in theprimary'mixing chambers seats on the bottom of such chamber, preflntingdownward flow through the channel The metering orifice 47 is drilled inthe ide o the channel 44 is plugged by a screw Each primary fuel nozzleis shown herein as provided with a main fuel outlet in the top of thenozzle and a secondary fuel outlet comprising two holes 54 and 55 formedin the vertlcal wall of the nozzle and diametrically opposite each otheras shown in Fig. 3. -At higher speeds there is suiiicient suction in theprimary mixing chambers to cause fuel to flow from the main fuel outletin the top of each primary nozzle, as well as from the holes 54 and 55.At 'idle or very low speed, however, there is insufficient suction tocause such a ow of fuel, the fuel at such time standing in the nozzle ata point between the top of the nozzle and the orifices 54 and 55,flowing connect with L-shaped passages formed in lthe manifold, theoutlet ends of such passages terminating in the side walls of thecentral branch of the manifoldv where they are connected with primarymixture pipes 'hereinafter described. The inlet ends of the primarymixture passages where the nozzles project into such passages are oflarger diameterthan the outlet ends thereof and between the inlet andoutlet end of each as'- sa e its cross-sectional area is'constricte asin icated at 64, such construction reducing the velocity of the aircurrent passing the nozzle for a purpose. hereinafter set forth.

of a screw 69, adjustable in the casting, to

prevent longitudinal movement ofthe said throttle. The primary mixturepassage 62 is in alignment with a tube which is received in a boss inthe branch 12, while the passages 61 and 63 communicate with pipes 71and 72, respectively. These pipesl are connected at one end to theoutlets of passages 61 and 63'while the other ends lof such pipesconnect with elbows 74 detachably secured to the manifold branches 11and 13, the outlet ends of such elbows being in alignment with tubes 7 5andV 76 which are secured inmanifold branches 11 and 13 respectively inany suitable manner.' Primary mixture is drawn by engine suction fromthe primary mixing chambers through the pipe connections abovedescribed, and tubes 70 and 75' to a main air chamber 8O formed in thehous ing 18. An air conduit 81 controlled by a valve mechanismhereinafter described con-v nects the air chamber with the main'airvmanifold while an orifice 82 in the floor of the air chamberpermits a flow of air from the chamber to the primary carburetors.

' When the carburetor is choked to start the engine the air valve 77 isheld against its i seat by means presently described to conipletelyclose the main air inlet. To provide sufficient air to carry thestarting fuel from the primary nozzles to the engine when thecarburetor-is choked as described an air inlet 83 is provided. Thisinlet is an elongated slot formed in a plate 84 secured to the housing18 as shown in Fig. 3.

' The main air valve 77 is adjustably secured on a stem 86 slidablymounted in al guide l sleeve 87 xed in the main housing 18. Surroundingthe guide sleeve 87 is a slidable sleeve 88, the lower end of which `hasa proj ecting disc 89 secured thereto, the disc providing aseat for theair valve spring 79. Means are provided for raising this sleeve toaposition where the upper end thereof will engage the air valve to holdit against its seat to choke the carburetor. This means comprises an arm90 secured to a rock shaft 91 rotatably mounted inthe wallfof the mainhousing 18. The armv at its inner end has two pins 92 and 93 securedtherein between which the disc 90` is received. The shaft 91 projectsthrough the wall of the casing and at its outer end is bent to form anarm 200.

having a hole 201 therein in which some form of operating connection,extending from a point convenient to the operator may be attached. Anadjustable stop screw 202 isreceived in a lug detachably secured to the'air horn asindicated in Fig. 2. By adjustment of the stop screw thenormal position of the sleeve 88 may be determined to regu* late thetension of spring 79. Ordinarily the stop screw is so adjusted that themain air valve willopen slightly during idling.

During operation-lat all engine speeds below that corresponding to avehicular speed of substantially 20-25 miles per hour on a level roadthe mixture formed in the primary carburetors is of properly combustibleproportions and such mixture is conveyed to the engine Without dilutionby admixture with additional air in the secondary `mixing chambers. Athigher engine speeds, unless means are provided toprevent such action,the velocity of the air current passingthe nozzles becomes so great thata velocity head is built upat the nozzles and increases to such a degreethat fuel is caused to iowifrom the nozzles rapidly enough to forma'primary mixture Which is super-rich infuel content.

To prevent this increase in fuel fiow the air passage 81 leading fromchamber 80 to the main air manifold is opened in 'a manner hereinafterdescribed, to permit a flow of air through the secondary airpassage.This admission of air through the secondary air passage not only dilutesthe mixture but also prevents as great an increase inair velocity at thenozzles as would otherwise occur.

Flow of air from the ychamber 80 to they secondary carburetors iscontrolled by two valves, a manually operated butterfly throttle 94 anda suction operated valve 95. The valve 94 is fixed on a shaft 96 whichis journalled for rotation in the walls of the housing 18, and isoperated simultaneously with throttle 65 through connections hereinafterdescribed. -The valve 95 is fixed to a shaft ,97' which is positionedofi' center with respect to the valve, a greater portion of the valvebeing below the shaft than above'. The shaft 97 is supported forrotation in the walls of the housing 18 and `is operated primarily bythe engine suction, its operation being controlled by devices describedlater.

The operating connections for the ythrottle valves will now bedescribed.. Fixed on the end of one of the throttlespindles 67 outsidethe housing 18 is an operating arm 98 having a hole in its free end tobe connected toI some suitable form of operating connection extending toa point convenient to the operator of the vehicle. This operating arm 98is connected through a lost motion connection to an arm 99 secured by asplit clamp to the end of shaft 96 outside the casing. An operating link100 is pivotally connected to the arm 98, and a pin 101 projecting fromthe free end of arm 99 projects through a slot 102 in the link 100. Aregulating screw 103 is threaded in lugs 104 projecting from theoperating link and may be adjusted to regulate the length of the slot102, the upper end of the said screw constituting the lower end of`sai-d slot. A tension spring 105 is connected at one end to the upperend of the link 100 and at its other end to the pin 101. The springtends to hold the pin 101 against the upper end of slot 102. lVith boththrottles closed the parts are in the position shown in Fig. 9, with thepin 101 in engagement with screw 103. As the operating arm 98 is rotatedin a clockwise direction to open the primary throttle valve 65 the link100 moves downwardly to a position where the upper end of slot 102strikes pin 101 before the operating arm 99 of the air throttle 94 ismoved so that the primary throttle is partly opened before the airthrottle begins to open. The screw 103 serves as a stop to limit theclosing movement of the primary throttle and adjustment of saidscrew-regulates the throttle opening at idling.

On opening movement of either throttle Valve the suction below the airvalve 7 7 is increased and the air valve is opened against the tensionof its spring permitting an inrush of air to the secondary mixingchambers which will be suiiicient to lean the mixture unless means areprovided to retard the opening movement of said valve. By retarding theopening of the valve the leaning of the mixture as well as fluttering ofthe air valve may be prevented. lIt will be understood, of course, thatopening of the air valve may be sufficiently retarded on opening of thethrottle to enrich the mixture for acceleration, but in this particularembodiment of the invention opening of the air valve is not retarded tothat extent.

To retard the opening movement of the air valve the lower end of thevalve stem 86 has secured thereto a piston 106 which slides in acylinder 107 formed in the casting 25. The

piston is securedto the stem l86 by means disclosed in the copendingcase above referred to,- a nut 109 holding the piston in place.

`The lower end of the cylinder is closed by a closure member 110, havinga valve controlled inlet (not shown) therein, and permitting free upwardmovement of said piston, but retarding the downward movement thereofandopening movement of the valve.

The dashpot cylinder 107 may be provided with a by-pass in its wallwhich allows liquid to pass around the piston when the piston passesbelow the upper end of said by-pass, thus relieving the dashpot. As thisby-pass forms no part of the present invention and its construction andfunction is fully described in the above mentioned application it is notshown herein.

lrVhcn the main vthrottle valve 94 is opened the suction in the chamber80 below the air valve 7 7 is so greatly increased that although thesuction at the nozzles is increased and at the same time the openingmovement of the main air valve is retarded to some extent to preventleaning of the mixture the additional air iiow into the secondary mixingchambers through the main air passage, past the throttle valve 94 wouldbe so rapid as to prevent any enrichment of the mixture imto providesufficient fuel for proper engine acceleration.

The opening movement of the air valve is retarded primarily forproducing at all times, when the throttle 94 opened, a sufficientpressure differential between the inlet and outlet ends of the primarymixing tubes to create a velocity of flow through such tubes greatenough to transport the primary mixture from the primary mixing chambersto the secondary mixing chambers almost instantaneously. In the devicedisclosed herein an accelerator pump forces, fuel for acceleration intothe primary mixing tubes to form a super rich mixture therein. It is aconsiderable distance from the point where fuel enters the primarymixture passages to the valve 95 relative to throttle 94: two resultsare accomplished, first the production of a high pressure differentialbetween the inlet and outlet ends of the primary mixtuge passages whichmaintains a high velocity of flow through such-passages at all timessecond the retarding of the inflow of pure air to the secondary mixingchambers. By maintaining the high velocity of flow through the primarymixture passages the timeinterval reuired for the primary mixture totravel the istance above referred to is greatly reduced.

At the same time the retardation ofthe air flow by means of valve 95increases the time interval necessary for pure air to reach thesecondary mixing chambers, so that these two time intervals approacheach other, in fact p primary mixture and the air flowingvpast throttle94 reach the secondary .mixing chambers at substantially the same time.

According to this invention means are provided to retard the opening ofthe valve 95 which comprises an arm 120 secured outside the housing 18to the end of shaft 97 on which the valve 95 is mounted. A rod 121 isbent at its upper end to forni a short horizontally extending leg 122which projectsthrough a suitable slot 123 in the free end of arm 120.The slot permits movement of the leg 122 relative to the end of arm 120as the latter moves in an arcuate path, enabling the rod t'o move in arectilinear path. Atits lower end the rod 121 is connected to a piston124 preferably by meansv of a flanged coupling memben 125 pinned to therod and a nut 126 screwed onsaid coupling member, the piston beingsecurely clamped between the iange on said coupling member and the nut.The piston has a close sliding fit within a cylinder 127 rovided withanattaching flange 128 projecting therefrom which is bolted to the housing18as shown in Fig. 8. A vent 129 is provided in the cylinder 127 toallow escape of air on descent of the piston and a spring 130 isreceived in said cylinder between its bot toni and the bottom of thepiston, said spring acting to normally hold the valve 95 closed.

lt will be noted that according to the present invention the valve 95 ispositioned anterior to the throttle 94 and the shaft 97 on which saidvalve is mounted is placed close to the floor of the passage 81, so thatthe valve when fully open lies flat on the licor of said passage, thepassage 81 being formed with a. flat bottom for some distance posteriorto said valve as indicated in Fig. 9 to permit the mounting of saidvalve as described.

When the throttle 94 is closed the engine suction is not communicated tothe valve 95 and the spring 130 holds the valve closed. As the throttle94 opens, however, the engine suction is communicated to points in thepassage anterior to the throttle and as soon as the throttle is openedsuihciently for the engine suction effective on said valve 95 to becomegreater than the force of the spring 130 the valve is opened, movingpiston 124.

downwardly and forcing the air in the cylinder 127 out through the smallhole 129. Owing to the small size of hole 129 it is impossible to lowerthe piston rapidly and the opening of the' air valve is thereforedelayed, no matter what the degree of opening of the throttle 94` maybe.- This retarding means is a simple, efficient and inexpensive form ofair dash pot. 'On closing of throttle 94 the spring 180 will lift the'piston and close valve 95. R

As previously stated the opening of the valve 95 is temporarily retardedon opening of the main air throttle accelerate the flow of rimarymixture sufficiently to prevent sai mixture from lagging behind the flowof air through the manifold duringthe acceleration period, thuspreventin the formation of a lean mixture at the secon ary mixingchambers during the acceleration period. In the ydevice disclosed inthis application the priv106 and cylinder 107 constitutes the pump whichoperates when the piston' moves downwardly on opening of the air valve.A fuel delivery conduit 140 is received at its lower end in a hole inthe cylinder 107 near the bottom thereof while the upper, outlet end ofsaid conduit connects with a fuel channel 141 in a block 142, secured inany desirable mannerrto the bottom ofthe distributor bloclr in aposition somewhat posterior to the primary throttle as indicated in Fig.3. The block 142 extends across all ofthe primary mixture passages andfuel passages 143, 144 and 145 formed in said block communicate withpassages 146, 147 and 148 drilled in the bottom wall of the distributorblock, and communicating with the primary mixture passages 61, 62 and 63respectively, as shown in Figs. 3 and 13. Two air channels 149-, one ofwhich is shown in 'F ig. 3 admit air to the fuel channel 141 theentering air forming an emulsion with the fuel which issues frompassages 146, 147 and 148 into the primary m1x' ture passages.

The reason for admission of air to the fuel channel 141 is to preventthe high suction maintained in the primary carburetors acting to drawfuel from the dash pot cylinder independently ofthe pumping action ofthe piston 106. 1t will be understood that under all conditions ofoperation a very con-` siderable degree of suction is maintained in theprimary mixing chambers and unless the fuel delivery passage between thedash pot cylinder and the primary mixture passages is vented toatmosphere at some point therein, this high suction would operate tolift fuel from the dash pot cylinder at all times, whereas it isdesirable to deliver fuel from the dash pot cylinder to the primarymixture passages only when the throttle is opened to cause downwardmotion of the piston 106. By admitting air to the fuel channel 141 thesuction effective to'lift fuel throuvh the conduit 140 is never greatenough to hft the fuel to the channel 141, but is sufficient to liftfuel only to some point intermediatethe dash pot cylinder and saidchannel preferabl to a ton 106 is in position to close the upper end 4ofthe by-pass. As soon as the by-pass is uncovered the pumping actionceases and further downward movement of the piston operates merely toforce fuel from the lower part of the cylinder through the by-pass tothe upper part of the c linder.

In addition to the a ove described devices operating to enrich themixture for acceleration means is provided for supplyin additional fuelat high speed by opening t e fuel `valve 49 previously referred to. Thismeans comprises an arm 150 pivoted at 151 on the outside of housing 18Vas shown in Fig. 8. Projecting from the opposite end of the arm 150, isa pin 152 which is receivedvin a bore in an enlarged head 153 into whichthe valve 49 is screwed. A cam 154is fixed on the spindle 67 projectingfrom the end of the throttle shaft opposite to that on which itsoperating arm 98 is secured, and cooperating with this, cam is a roller155 mounted for rotation on a pin projecting from theearm 150. Aconsiderable portion of the cam is concentric relative to its operatingshaft, so that it is ineffective to raise arm 150 to open the fuel valveuntil a certain predetermined speed is reached, for example an enginespeed corresponding to a vehicular speed of 20-25 miles per hour. Byusing a cam of different shape the engine speed at which the fuel valvebegins to open may be regulated as desired. Also by adjusting the valvein its head153 the normal position of e valve prior to the opening ofsaid valve y arm 150 may be determined.

The secondary mixing chambers comprise Venturi tubes 160 (as shown) orother fiow accelerating elements. these venturis 160 which are identicalin construction and are positioned in the branches 11, 12 and 13 of themanifold 10, in such relation to the primary mixing tubes, that thepoint.` of greatest depression or suction in each Venturi tube isimmediately adjacent the outlet end of the primary mixture tubeassociated therewith. Each venturi is provided .with an annularprojecting rib 161 which fits, when the manifold is attached to theengine block, both inthe engine intake port and in a recess 162 in theend of the associated branch of the manifold the rib engaging shoulders163 and 164 in the manifold and intake port respectively when theventuri is in position. A channel 165 is There are three of formed inthe outer wall of said venturi at the bottom of said element when t-hedevice is assembled,I to permit any fuel which precipitates out of themixture and collects on the wall of the manifold branch to flow into theengine intake port. The Venturi tubes,

cause the air entering the air manifold to move past the ends of t'ubes70, 75,'and 76 at high velocity creating in each of the tubes a highsuction at all times'.

It will be understood that while the device,

for retarding the passageof air through the secondary air passage onopening of the air throttle, which constitutes the present invention, isdisclosed, for convenience, in this application as embodiedin a chargeforming device having means for enriching the primary mixture,theinvention is in .no way limited to` such a charge forming device. Suchinvention will produce desirable results when embodied in a chargeforming devlce in which enriching fuel is not injected into the primarymixture concurrently with the retardation of air flow through thesecondary air passage. It will be clear that such air should not bepermitted to reach the secondary mixing chambers on opening of the airthrottle, before the increased quantity of primary mixture resultingfrom opening ofthe primary throttle reaches said mixing chambers,Whether said primary mixture is in-v creased in vfuel content or not.

While the form of embodiment of the present invention as hereindisclosed, constitutes a preferred form, it is to be understood thatother forms might be adopted, all coming within the scope of the claimswhich follow.

What is claimed is as follows:

1. In ay charge forming device for a multicylinder engine having aplurality of intake ports the combination of a main air manifold havingbranches leading to said intake ports and forming secondary mixingchambers, a plurality of primary carburetors for supplying fuel mixtureto said secondary mixing chambers, a single air intake passage admittingauxiliary air to all of said secondary carburetors,'a throttle forcontrolling the flow through said passage and a`suction op-A eratedvalve in said passage for modifying the effect of said throttle.- 3. `Ina charge forming device for a multicylinder engine having a plurality ofintake ports', the combination of a main air inanifold having branchesleading to said intake ports and forming secondary mixing chainbers, aplurality of primary carburetors for supplying fuel mixture to saidsecoi'idai'y mixing chambers, a single air intake passage admittingauxiliary air to all of said secondary carburetors, a throttle forcontrolling the flow through said passage, a suction operated valve insaid passage for modifying the effect of the throttle and means forretai-ding the opening movements of said valve.

4. In a charge forming device. for a multicylinder engine having aplurality otl intake ports, the combination of a main air inanifoldhaving branches leading to said intake ports and forming secondarymixing chambers, a plurality of primary carburetors for supplying fuelmixture to said secondary mixing chambers, a single air intake passageadmitting auxiliary air to all of said secondary carburetors,.a throttlefor Controlling the flow through said passage, a suction operated valvein. said passage for modifying the etliect of the throttle and a dashpot for retarding the opening movements` of said valve.

5. A charge forming device for internal combustion engines hav-ing incoinbnation a plurality of secondary mixing chambers, a plurality oiprimary carburetors for supplying fuel mixture thereto, conduits forconveying the primary mixture to said second-A ary mixingchambers, meansin said secondary mixing chambers for maintaining a high vacuum at theoutlets ot' said primary mixture conduits, a passage for applyingauxiliary air to all said secondary mixing chambers only under certainoperating conditions and automatic means for retarding the flow or" airthrough said passage when the latter becomes eective to preventreduction of the vacuum at the outlets of said primary mixture passages.

6. A charge forming devicel for internal combustion engines having incombination a plurality of secondary mixing chambers, a plurality ofprimary carburetors for supplying 'fuel mixture thereto, conduits forconveying the primary mixture to said secondary mixing chambers, meansin said secondary.

mixing chambers for maintaining a high vacuum at the outlets of saidprimary mixture conduits, a passage for supplying auxiliary air to allsaid secondary mixing chambers, a normally closed throttle in saidpassage, means for opening said throttle at a predetermined enginelspeed,- and automatic means for retarding the iow ot air through ,saidpassage when the throttle is openeihto prevent reduction oit the vacuumat the outlets of the primary mixture passages.

7. A charge forming device for internal combustion engines comprising aplurality of secondary mixing chambers, a plurality of primarycarhuretors for supplying fuel mixture thereto, a primary throttlecontrolling the flow from all the primary caburetors, a secondary airpassage for supplying auxiliary air to all' said secondary carhuretors,a secondary throttle controlling the How' of air therethrough. meansoperated by the primary throttle for opening said secondary throttleafter said primary throttle has opened a predetermined amount, and meansfor retarding the flow of air through the secondary air passage, onopening movement of the secondvary throttle.

8. A charge forming device for internal combustion engines comprising, aplurality of secondary mixing chambers, a plurality of primarycarburetor-s in which a primary mixture of fuel and air is formed fordelivery to the secondary mixing chambers, a secondary air passageadapted to supply auxil- -iaiy air to all'of said secondary mixingchambers, a single main air inlet supplying air to all the primarymixing chambers, a/tlirottle for controlling the supply of mixture, anddevices for retardingthe'flow of air through the main air inlet andsecondaryl air passage on opening movement of' the throttle.

9. Av charge forming device for internal combustion engines comprising,a plurality of secondary mixing chambers, a plurality of primarycaiburetors in which a primary mixture of uel and air is fori'ned fordelivery to the secondary mixing chambers, a secondary air passageadapted to supply auxiliary air to all of said secondary mixingchambers. a single main air inlet supplying air to all the primarymixing chambers. a throttle for controlling the supply of mixture,nieansitoiretarding the fioiv of air through the main air inlet onopening movements of the throttle under all operating conditions,andmeans for retarding the flow of air through the secondary air passage onopening movements oi the throttle under certain operatingconditionsonly.

10. A charge forming device for internal combustion engines comprising,a plurality of secondary mixing chambers, a plurality or primarycarburetors in which a primary ymixture offuel and air is formed fordelivery -for modifying the effect of the air throttle.

1l. A charge forming device for internal combustion engines comprising,a plurality Y of secondary mixing chambers, a plurality of primarycarburetors in which a primary mixture of fuel and air is formed fordelivery to the secondary mixing chambers, a secondary air passageadapted to supply auxiliary air to all of said secondary mixingchambers, a single main air inlet supplying air to all the primarymixing chambers, a prilnary throttle for controlling the How of primarymixture from all of the primary carburetors, an air throttle forcontrolling thel flow through the secondary air passage and an automaticsuction operated valve in said air passage. A

12. A charge forming device for` interna-l combustion enginescomprising, a plurality ot secondary mixing chambers, a plurality ofprimary carburetors in which a primary mixture of fuel and air is formedfor deliver to the secondary mixing chambers, a secon ary air passageadapted to supply auxiliary air to all of said secondary mixingchambers,a single main air inlet supplying air to all the primary mixingchambers, a primary throttle for controlling the flow of primary mixturefrom all of the primary carburetors, an air throttle for controlling theflow through the secondary air passage, an automatic suction operatedvalve in said air passage, and means for temporarily retarding theopening movement of said valve on opening movement of the air throttle.

13. A charge forming device for internal I combustion enginescomprising, a plurality of secondary mixing chambers, a plurality ofprimary carburetors in which a primary mixture of fuel and air is formedfor delivery to the secondary mixing chambers, a secondary air passageadapted to supply auxiliary air to all of said secondary mixingchambers, a single main air inlet supplying 'air to all the primarymixing chambers, a primary throttle for controlling the iiow of primarymixture from all of the primary carburetors, an air throttle forcontrolling the flow through the secondary air passage, common operatingmeans for opening said primary and air throttles, and means fortemporarily retarding the How of air through the secondary air passageon opening movements of the air throttle.

14. A charge forming device for internal combustion engines comprising,a plurality of secondary mixing chambers, a pluralityn of primaryearburetors in which a primary mixture of fuel and air is formed fordelivery to the secondary mixing chambers, a secondary air passageadapted to supply auxiliary air 'to all of said secondary mixingchambers, a single main air inlet supplying airtoall the primary mixingchambers, a primary y throttle for controlling the fiow of primarymixture from all of the primary earburetors, an air throttle forcontrolling the How through the secondary air passage, common operatingmeans for opening said primary In testimony whereof I hereto alix mysignature.

YVILFORD H. TEETER.

